My girlfriend has an '04 Civic (automatic) with this tapping and slight squeak that almost sounds like a tapping injector. The noise is coming from the top, back side of the engine (near the throttle lever).

Obviously the car is going in for warranty reasons. However, I'm curious as to what the hell this noise is. This noise happens when the car is cold, and stops after the car has been warmed up for 15 to 20 minutes.

What do you think this might be? Thanks.